DESCRIPTION: Otitis media (OM) is the most prevalent disease among young children and costs society about $1 billion dollars annually (NIDCD Annual Report, 1991). Eustachian tube (ET) dysfunction has long been implicated as a contributory factor in OM. However, the specific morphological features of the ET which may result in tubal dysfunction and subsequent middle ear (ME) disease have not been identified. This proposal will examine morphological features of the ET-ME in 3 groups of individuals that are susceptible to OM and have distinctive patterns of ME dysfunction: children, cleft palate (CP) and Downs syndrome (DS) patients. Histopathological features in these groups will be compared to the results of analysis of the same structures in normal adults. Sando and colleagues have developed a unique technique for harvesting the temporal bone and entire ET-ME system as a single specimen. These researchers presently have 109 of such specimens available for the proposed study; with funding, it is estimated that 20 specimens per year can be added (from children, CP and DS patients). The studies to be performed include standard otopathological examination (i.e., H&E), special staining in celloidin and immunohistochemical techniques. Anatomical/histopathological features to be examined and quantified include: 1) the spatial relations between the ET and associated structures; 2) variations in tissue organization and cytology; 3) elastin content of cartilage and connective tissue as an indicator of tissue pliability; 4) patterns of expression of myosin isoforms in the tensor veli palatini and levator veli palatini muscles as an indicator of muscle function; and 5) T-cells, B-cells, and macrophages in the ET lumen, ET connective tissue, and mucosa-associated lymphoid tissue as an indicator of immunological susceptibility. By comparing results of these analyses across subject groups, potential risk factors will be identified for the development of OM and strategies can be developed for prevention.